A part of understanding climate change is knowledge of the carbon cycle. However, much misunderstanding regarding climate change is involved with the amount of time that carbon remains in the atmosphere. Many climate deniers try to refute clear evidence of climate change because carbon molecules reside in the atmosphere for a relatively short time. However, climate change is not irrelevant because of atmospheric carbon dioxide.
If all carbon emissions were to cease today, it would take the remainder of the next century to rid the atmosphere of extra carbon dioxide. Even if this did take place and all CO2 was absorbed, at least twenty percent of the carbon dioxide would still be in the earth’s atmosphere for at least tens, if not thousands, of years.
The global carbon cycle involves the absorption and release of carbon dioxide in the atmosphere, and oceans, soils, and organic matter all play a role in the “catch and release” of carbon dioxide by our atmosphere. Then, one must take into consideration emissions from fossil fuel combustion as well as changes to the way we use land.
One must consider how the combustion of fossil fuels influences the way that the atmosphere absorbs carbon dioxide. Every year approximately 230 gigatons of carbon dioxide is released into the atmosphere. Around 230 gigatons of carbon dioxide is absorbed by the atmosphere. These numbers are not counting how fossil fuel emissions change the rate of carbon dioxides being released into the atmosphere, however.
Once humans started burning fossil fuels, the amount of carbon dioxide in the atmosphere spiked upwards drastically. This is proof that the human use of fossil fuels is having a direct influence over how much carbon dioxide goes into the atmosphere.
Ironically, there ARE some fossil fuels that are NOT being accumulated in the atmosphere. About half of the annual emissions from fossil fuels are being absorbed by the ocean and by vegetation. This is called airborne fraction, and it is a hotly debated topic.
Then there are those who simply don’t understand how atmospheric carbon is absorbed. These individuals believe that the average molecule of atmospheric carbon will be naturally absorbed after three or four years. This is where the residence time comes in to play. It is how long the full stock of atmospheric carbon will remain in the atmosphere that matters as opposed to one individual molecule in the atmosphere.
Scientists use something called models of carbon sink behavior in order to measure how long the atmospheric carbon stock will remain. These provide averages as to how long atmospheric carbon stock will remain based on previous knowledge. Researchers believe that about fifty percent of the net anthropogenic pulse will be absorbed over a period of fifty years; they also believe within one hundred years, about seventy percent of this atmospheric carbon will be observed. One scientist has posited that, using this model, carbon can last in the atmosphere up to 35,000 years.
Even if all emissions were removed from the earth at present, at least ten percent of global warming will continue for thousands of years to come.